linux-kernel - Re: [PATCH 04/10] x86: mce: fix error handling

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Message-ID: <4C51538C.1090803@bfs.de>
Date:	Thu, 29 Jul 2010 12:10:20 +0200
From:	walter harms <wharms@....de>
To:	Andi Kleen <ak@...ux.intel.com>
CC:	Vasiliy Kulikov <segooon@...il.com>,
	kernel-janitors@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Borislav Petkov <borislav.petkov@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/10] x86: mce: fix error handling



Andi Kleen schrieb:
> 
>> IMO memmory allocation fails are dangerous in kernel mode. As it is
>> probably not exploitable because of boot time, it can destroy some
>> sensitive data like dirty disk caches those are going to be written on
>> disk.
> 
> It's true for runtime, but not for normal boot time.
> 
> Anyways if it happens on boot time the only thing you can do is panic,
> but someone else
> will likely panic anyways for you. Just ignoring it like your patch
> effectively does
> (because nothing will ever look at the ENOMEMs for an initcall) is wrong
> though
> In this case it's actually better to oops like the original code does.
> 
> BTW even with your patch likely later code will crash anyways because it
> doesn't
> expect init code to fail.
> 

NTL it is nice to have a error message. for users it is worse if you crash suddenly
with out warning than having a crash with "OOM" before because it gives you a clue
what is going on.
short:
please think of users that are not kernel developers give them a hint what went wrong.

to make thinks more easy on boot we could replace kalloc() with kmalloc_or_die().
When anyone runs out of mem on boottime you can panic() instantly.

just my to cents,
 wh

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